Carbon dioxide emissions from power plants can be detrimental to the environment. In general, carbon dioxide emissions from coal-fired power plants may be reduced by increasing the overall plant efficiency, which in turn may be realized by (1) increasing the steam temperature and pressure; (2) reconfiguring the steam cycle from single reheat to double reheat; or (3) reducing the back pressure of the steam condenser. These steps, however, may be difficult to achieve in practice. For example, the steam temperature and pressure are limited by the temperature and stress that the current material used in steam production can withstand. Reconfiguring the steam cycle from single reheat to double reheat may require rearranging the heat surfaces inside the boiler in a complicated way, rendering the implementation difficult. Finally, the back pressure of the steam condenser depends on numerous factors such as the equipment sizes of the condenser and the cooling tower that recirculates cooling water, and the ambient air conditions, all of which need to be suitably adjusted.
Carbon dioxide emissions of fossil-fuel-fired power plants may be effectively reduced by capturing the carbon dioxide from the flue gas, and storing the captured carbon dioxide. It is known to capture carbon dioxide at high pressures in natural-gas purification, with an absorbing reagent such as an aqueous solvent. The flue gas in fossil-fuel-fired power plants, however, typically contains about 12% to about 14% of carbon dioxide, which is lower than that of the flue gas in natural-gas purification. The lower concentration of carbon dioxide in the flue gas of fossil-fuel-fired power plants reduces the driving force for the carbon dioxide absorption. Thus, a need exists for more effective capture of carbon dioxide from the flue gas of fossil-fuel-fired power plants.
Once the carbon dioxide is captured by being absorbed in the absorbing reagent, the absorbing reagent will need to be regenerated for continued use. The regeneration of the absorbing reagent takes energy, however, reducing the power output of the plant. To account for the reduced power output due to the regeneration of the absorbing reagent, there has developed a need for a power plant with an increased power output.